As a conventional heating cooker employing a range hood, an apparatus body 501 having a function of range hood is mounted on a kitchen wall 502, as shown in FIG. 11 through FIG. 13. That is, the apparatus body is placed in a very tight and restricted space where it is surrounded by a ceiling (not shown) above, another heating cooker 503 underneath, and for example storage cabinets 504 on both sides. The conventional structure is described below by referring to the drawings.
The apparatus body 501 comprises three sections, namely: a range hood section having a ventilating fan 505 and others; a heating section having a heating chamber 506 wherein food is placed and heated; and a cooling section having a cooling fan 509 and others provided to maintain a high frequency generating apparatus 507 such as a magnetron tube for heating and cooking the food and a control device 508 at temperature below a predetermined level.
It is therefore desirable to equip the apparatus body 501 with a ventilating fan having a large volume of exhausting air with a low noise, a heating chamber of a large capacity capable of heating and cooking a large mass of food, and a compact and efficient cooling means. On the other hand, a pace available for installation of the apparatus body 501 in kitchen is limited, thereby restricting external dimensions of the apparatus body 501, resulting in certain problems as described below.
First, the range hood section is described. In the prior art, heating cookers of this kind are provided with, over the heating chamber 506 wherein food is placed, a wave-guide 510 which transmits high frequency energy generated by the high frequency generating apparatus 507, and a feeding port 511 on a top wall of the heating chamber 506 to supply the high frequency energy into the heating chamber 506. On the other hand, the apparatus body 501 has intake openings 512a and 512b of the apparatus body on its bottom wall to draw air containing gaseous product generated by the second heating cooker 503 such as a gas cooking stove, and the drawn air is exhausted outside by the ventilating fan 505 located above the heating chamber 506 through an exhaust opening 513 of the apparatus body and an attached air duct. The ventilating fan 505 has intake openings 514a and 514b of the ventilating fan at its suction side and an exhaust opening 515 of the ventilating fan at its venting side. The heating chamber 506 is approximately symmetrical in its shape and has the feeding port 511 in approximate center of the upper wall of the heating chamber 506, in order to obtain an even distribution of the high frequency energy on both sides within the heating chamber 506 for heating the food uniformly. Also, as a general practice the exhaust opening 513 of the apparatus body is located in the upper rear corner of the apparatus body 501, because a direction of the exhaust air-flow may vary between rearward and upward depending upon an installation of the apparatus body 501. It is also the general practice that the ventilating fan 505 is positioned adjacent to the exhaust opening 513 of the apparatus body, in the upper rear corner of the apparatus body 501, as described in U.S. Pat. No. 4,786,774, so as to minimize an air-flow resistance from the exhaust opening 515 of the ventilating fan to the exhaust opening 513 of the apparatus body and to assure an efficient exhausting. Furthermore, the ventilating fan 505 is normally positioned on top of and in approximate bilateral center of the apparatus body 501, next to the wave-guide 510, so that the distances from the two intake openings 512a and 512b of the apparatus body are nearly equal, thereby the two intake openings 512a and 512b of the apparatus body suck the gaseous product in substantially equal quantity. As a result, the drawing efficiency is increased.
In the conventional heating cooker, however, if an outer diameter of the ventilating fan 505 is to be increased in order to enhance the exhausting air flow, the upper wall of the heating chamber 506 must be lowered to obtain a space to fit the ventilating fan 505, which consequently requires the apparatus body 501 to be extended vertically by lowering the bottom wall of the heating chamber 506 in order to also maintain the space large enough to contain a sizable food. If the apparatus body 501 is dimensionally increased thereby reducing a space below the apparatus body 501, placement of a large-sized pan 517 on the second heating cooker 503 such as a gas cooking stove is restricted. This is where a problem exists, i.e., a spatial limitation restricts the degree of freedom in designing, making it a difficult task. In particular, as described in U.S. Pat. No. 4,786,774 a structure, in which the ventilating fan 505 is rotated for changing a direction of the exhausting air-flow upward, rearward or forward, requires a square space in cross sectional dimensions, which imposes another problem of further restricting the designing.
Second, the cooling section for cooling off a machinery compartment 518 is described. A conventional heating cooker employing a range hood of this kind, as shown in FIG. 12, provides cooling air drawn from an intake opening 519 of the machinery compartment located in the upper part of the apparatus body 501 to the cooling fan 509 disposed on rear wall of the machinery compartment 518 and exhausts the air through an exhaust opening 520 of the machinery compartment located in the upper part of the apparatus body 501, and at the same time, the gaseous product generated by the second heating cooker 503 situated below is ventilated by drawing it through the intake openings 512a and 512b of the apparatus body and exhausted outside by the ventilating fan 505. As the depth of the machinery compartment 518 is extensive, a ventilation air path 521 is provided on the side of the machinery compartment 518, as described in U.S. Pat. No. 4,886,046.
In the conventional heating cooker employing a range hood, however, a problem of a low exhausting efficiency exists, because the cooling fan 509 is stored in a rear part of the machinery compartment 518, which causes a depth of the machinery compartment 518 so wide that it obstructs the ventilation air path 521 of the ventilating fan 505. Furthermore, if a volume of the heating chamber 506 is increased, it forces the machinery compartment 518 to be moved toward the ventilation air path 521, resulting in a narrower ventilation air path 521 and a longer path between the ventilating fan 505 and the ventilation air path 521, and to causes a problem of further lowering the exhausting efficiency. In particular, the structure as described in U.S. Pat. No. 4,886,046, where temperature detecting means is arranged in vicinity of the control device 508 to lower a temperature of the control device 508 by automatically operating the ventilating fan 505 when a detected temperature reaches at a set-temperature, has a problem that the control device 508 tends to heat up fast, and is liable to exceed an allowable temperature limit of its components if the exhausting efficiency is lowered. There is yet another problem that lowers the exhausting efficiency due to this structure in that the intake opening 519 of the machinery compartment and the exhaust opening 520 of the machinery compartment adjoin each other, so that the exhausted air tends to be redrawn for recirculation into the intake opening 519 of the machinery compartment.
Furthermore, the conventional heating cooker employing a range hood comprises a louver 522 over the exhaust opening 513 of the apparatus body, as shown in FIG. 13, through which air is exhausted out of the machinery compartment. However, this structure of the conventional heating cooker tends to soil the louver 522 with gaseous product generated by the food being heated. If an opening area of the louver 522 is reduced so as to make the soil inconspicuous, a volume of air exhausted from the heating chamber 506 and the machinery compartment 518 is also reduced, which on the other hand promotes soiling of an interior of the heating chamber 506 and makes the machinery compartment 518 liable to exceed an allowable temperature limit of the components therein.